This study will address whether patients with fibromyalgia (FM) have a normal endocrine response to the stress of exercise. Subjects will be 12 FM and 12 healthy subjects with low aerobic fitness. Aerobic fitness, growth hormone and cortisol will be measured before and after graded exercise on a treadmill. During a second testing, the same procedures will be used with the addition of pyridostigmine bromide 60 mg (to inhibit somatostatin tone) one hour before treadmill testing.